Ancilla-Assisted Calibration of a Measuring Apparatus
G. Brida, L. Ciavarella, Ivo Pietro Degiovanni, Marco Genovese, Alan L. Migdall, M. G. Mingolla, Matteo G. A. Paris, Fabrizio Piacentini, Sergey V. Polyakov · Physical Review Letters · 2012
A quantum measurement can be described by a set of matrices, one for each possible outcome, which represents the positive operator-valued measure (POVM) of the sensor. Efficient protocols of POVM extraction for arbitrary sensors are required. We present the first experimental POVM reconstruction that takes explicit advantage of a quantum resource, i.e., nonclassical correlations with an ancillary state. A POVM of a photon-number-resolving detector is reconstructed by using strong quantum correlations of twin beams generated by parametric down-conversion. Our reconstruction method is more statistically robust than POVM reconstruction methods that use classical input states.